Cosmic-Ray Electrons Near Sea Level and at Mountain Altitudes

A cloud chamber containing aluminum and lead plates has been used to study the intensities and energies of cosmic-ray electrons as a function of altitude and zenith angle. The energy distribution is found to be approximately independent of altitude and zenith angle. The decrease of electron intensity with zenith angle is found to be much less than has been reported by investigators using counter telescopes. The increase of the vertical intensity with altitude is found to be slightly smaller than previously reported. The numbers of electrons resulting from decay and collision processes of $\mu$ mesons have been calculated and subtracted from the observed numbers. The residual electrons have an exponential altitude dependence with an absorption length of 135±15 g ${\mathrm{cm}}^{-2\mathrm{}}$, and a zenith-angle dependence which is much less steep than would be expected if they preserved the directions of the primary particles from which they originate.